This is an amended application addressing issues raised in the IRQ Summary Statement of 8/12/04. Support is requested for a three-year period to conduct a study of HIV prevalence, STI prevalence, and drug and sexual HIV risk behaviors in a random sample of 800 homeless mothers in New York City. The study's qualitative and quantitative components address the gap in information on HIV risk in this fast rising subgroup of the adult homeless in the United States. Homeless mothers possess many characteristics associated with HIV risk behaviors, including childhood sexual and physical abuse, substance abuse, psychiatric disorder, domestic violence, and poor social support. Although HIV infection is significant among the adult homeless, HIV and STI prevalence has not been studied among homeless mothers. HIV prevalence will be determined with the OraSure HIV test based on oral mucosal samples. STI testing for chlamydia, gonorrhea, and trichomoniasis will be based on urine and vaginal swab samples. The research team will be responsible for pre and post test counseling, test results, and treatment for positive assays. Study aims include examining the relationship between HIV prevalence, STI prevalence, and HIV drug and sexual risk behaviors and homelessness, probing the extent to which risk behaviors are influenced by persistent residential instability. Guided by an integrated ecological framework, the study will investigate the relationship of multiple levels of risk and protective factors, including childhood sexual and physical abuse, mental illness, substance abuse, domestic violence, HIV knowledge and attitudes, and social support, to drug and sexual HIV risk behaviors and chronic homelessness. The study will inform the design of HIV risk behavior preventive interventions appropriate to the life circumstances of homeless mothers.